1. Field of the Invention
This invention is useful in the field of medicine, and relates to novel indolopyrrolocarbazole derivatives inhibiting proliferation of antitumor cells and exhibiting an antitumor effect, a process for preparation thereof and a use thereof.
2. Description of the Related Art
In the field of cancer chemotherapy, many compounds are already put to practical use as an antitumor agent. However, the effect thereof on various kind of tumors is not always adequate, and the problem of resistance of tumor cells against these drugs makes clinical use of these antitumor agents complicated [refer to The 47th Annual Meeting of Japanese Cancer Association Article, pages 12 to 15 (1988)].
In such state of things, development of novel carcinostatic substances is always desired in the field of cancer therapy. Particularly, substances are necessitated which overcome resistance against existing carcinostatic substances and exhibit effectiveness against such kinds of cancers on which existing carcinostatic substances cannot exhibit sufficient effects.
In the light of such present state of things, the present inventors widely screened microbial metabolic products, as a result, found a novel antitumor activity-possessing compound BE-13793C (12,13-dihydro-1,11-dihydroxy-5H-indolo[2,3-a]pyrrolo[3,4-c]carbazole-5,7( 6H)dione), and disclosed it [refer to Japanese Laid-Open Patent Publication No. 20277/1991 and J. Antibiotics, 44, 723-728 (1991)].
Thereafter, the present inventors created indolopyrrolocarbazole compounds having an excellent antitumor activity by chemically modifying BE-13793C, and disclosed them (refer to PCT/WO91/18003).
For the purpose of creating compounds having a further excellent antitumor activity by chemically modifying previously disclosed indolopyrrolocarbazole antitumor compounds, the present inventors synthesized many indolopyrrolocarbazole derivatives, investigated their antitumor activity, and as a result, now, found that a series of compounds represented by the following general formula are novel compounds having an extremely excellent antitumor activity.